This invention relates to the delivery of compositions to the lung.
The lungs are large, multi-lobed organs located in the chest, with each lung (i.e., the right and left lung) composed of three main components: the bronchial tubes, the pulmonary arteries and veins, and the pulmonary parenchyma. The main blood inflow into the lungs is from the pulmonary trunk, which sends unoxygenated blood from the right ventricle of the heart. The pulmonary trunk divides into the left and right pulmonary arteries, which further branch to supply arteries to each of the lobes and segments of the left and right lung, respectively. Blood flowing through these arteries reaches the alveoli of the lungs where red blood cells are separated from air only by a thin membrane of alveolar-lining cells and endothelial cells of the capillaries. Here, oxygen is picked up and carbon dioxide discarded. Oxygenated blood then returns to the left atrium of the heart via the pulmonary veins.
Although there is only one pulmonary artery supplying each lung, there are typically two pulmonary veins per lung (i.e., two pulmonary veins for the right lung, and two pulmonary veins for the left lung). The schematic representation of the lungs shown in FIG. 1 depicts the major blood vessels supplying and draining the left and right lungs. FIG. 2 provides a schematic representation of the left and right pulmonary arteries and veins as they relate to the flow of blood through the heart.
Given their crucial role in the delivery of oxygen to cells throughout the body, any impairment of the functioning of one or both of the lungs through disease or damage is a serious health consideration. Diseases of the lung may be congenital, or may be induced or exacerbated by environmental factors. Air pollution, cigarette smoke, and other harmful air-borne agents (e.g., asbestos) can contribute to a variety of lung diseases including, without limitation, chronic airflow obstruction, pneumoconiosis, pneumonia, restrictive lung disease (also known as infiltrative lung disease), and primary or metastatic lung cancer. Hence, methods for facilitating delivery of a therapeutic composition (e.g., a drug) to the lung would be useful in treating, or at least alleviating the symptoms of, a lung disease.